Reactor and safety method for a reactor for the event of a meltdown of the core

A safety method for a pressurised water nuclear reactor for the event of a meltdown, at least partially, of a core of the reactor with the formation of a corium bath, the reactor comprising, during an operation phase, at least:

• a primary circuit in which a water-based primary fluid is intended to circulate, the primary circuit being configured so that the primary fluid penetrates into a vessel of the reactor and crosses the core contained within the vessel in order to extract heat produced by the core,
• a secondary circuit, in which a water-based secondary fluid is intended to circulate, the secondary circuit being fluidly isolated from the primary circuit, and comprising at least one steam generator, the secondary circuit being configured so as to absorb heat from the primary circuit and transform it, at least partially, into steam in the steam generator,
• wherein the method comprises at least the following step in response to a detection of an event characterising a meltdown, at least partially, of the core of the reactor with the formation of a corium bath in a bottom of the vessel and with the formation of a liquid metallic layer at the surface of the corium bath:
• break-up by explosion of the fluidic insulation to set the secondary circuit in fluidic communication with the primary circuit so that the secondary fluid follows the primary circuit to flow inside the vessel over said liquid metallic layer of the corium bath.